1. Field of the Invention
This invention relates to a method for manufacturing TFT (Thin Film Transistor), and particularly relates to a method for manufacturing TFT that has high transmittance.
2. Description of the Prior Art
In fabricating TFT (Thin Film Transistor) LCD (Liquid Crystal Display) panel utilizing LTPS (Low Temperature Polycrystalline Silicon) technology, because the mobility of electrons can be greatly raised, the manufacture of high quality TFT-LCD panel is enabled, and the cost is lowered by reducing the number of connecting lines. Usually, the silicon nitride (SiNx) is utilized in the LTPS technology to form the interlayer or the passivation layer to been proceed with the hydrogenation process. The LTPS technology is designed to fabricate the LCD panel having high transmittance and high aperture rate, but the silicon nitride (SiNx) layer will lower the transmittance of the LCD panel. So the frequently utilized silicon nitride (SiNx) layer in the LTPS technology will degrade the performance of the LCD panel fabricated by the LTPS technology.
In the prior art LTPS technology utilized to form the TFT LCD, the silicon nitride layer is necessary for the hydrogenation process employed to improve the characteristic of the fabricated TFT panel. However the silicon nitride layer utilized in the LTPS technology reduces the transmittance of the LCD panel fabricated by the LTPS technology. The degradation mentioned above can be ignored when the request for the performance of the fabricated LCD panel is not so high. But, when the request for the resolution of the LCD panel is getting bigger, the request for transmittance of each pixel of the fabricated LCD panel is getting higher.
In the tide of high resolution, even a little degradation in transmittance of each pixel of the LCD panel will greatly reduce the transmittance of the entire LCD panel. When the request for the resolution of the LCD panel is not so high, the worse performance of the LCD panel can still be ignored. So the silicon nitride layer is still necessary in the fabricated TFT LCD. However, with the need for the transmittance and performance getting greater, the problem resulting from the silicon nitride layer must be resolved without causing other manufacturing problems.